Organic electroluminescent device

ABSTRACT

The present invention relates to organic electroluminescent devices comprising a light-emitting layer B comprising a triplet-triplet annihilation (TTA) material, a thermally activated delayed fluorescence (TADF) material and a near-range-charge-transfer (NRCT) emitter material, which exhibits a narrow—expressed by a small full width at half maximum (FWHM)—emission. Further, the present invention relates to a method for obtaining a desired light spectrum and achieving suitable (long) lifespans of an organic electroluminescent device according to the present invention.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/814,083, filed Mar. 10, 2020, which claims priority to and thebenefit of European Patent Application No. 19164281.8, filed on Mar. 21,2019, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present invention relates to organic electroluminescent devicescomprising a light-emitting layer B comprising a triplet-tripletannihilation (TTA) material, a thermally activated delayed fluorescence(TADF) material and a near-range charge transfer (NRCT) emittermaterial, which exhibits a narrow—expressed by a small full width athalf maximum (FWHM)—emission. Further, the present invention relates toa method for obtaining a desired light spectrum and achieving suitable(long) lifespans of an organic electroluminescent device according tothe present invention.

DESCRIPTION

Organic electroluminescent devices containing one or more light-emittinglayers based on organics such as, e.g., organic light emitting diodes(OLEDs), light emitting electrochemical cells (LECs) and light-emittingtransistors gain increasing importance. In particular, OLEDs arepromising devices for electronic products such as e.g. screens, displaysand illumination devices. In contrast to most electroluminescent devicesessentially based on inorganics, organic electroluminescent devicesbased on organics are often rather flexible and producible inparticularly thin layers. The OLED-based screens and displays alreadyavailable today bear particularly beneficial brilliant colors, contrastsand are comparably efficient with respect to their energy consumption.

A central element of an organic electroluminescent device for generatinglight is a light-emitting layer placed between an anode and a cathode.When a voltage (and current) is applied to an organic electroluminescentdevice, holes and electrons are injected from an anode and a cathode,respectively, to the light-emitting layer. Typically, a hole transportlayer is located between light-emitting layer and the anode, and anelectron transport layer is located between light-emitting layer and thecathode. The different layers are sequentially disposed. Excitons ofhigh energy are then generated by recombination of the holes and theelectrons. The decay of such excited states (e.g., singlet states suchas S1 and/or triplet states such as T1) to the ground state (S0)desirably leads to light emission.

In order to enable efficient energy transport and emission, an organicelectroluminescent device comprises one or more host compounds and oneor more emitter compounds as dopants. Challenges when generating organicelectroluminescent devices are thus the improvement of the illuminationlevel of the devices (i.e., brightness per current), obtaining a desiredlight spectrum and achieving suitable (long) lifespans.

There were attempts to improve photophysical properties ofelectroluminescent devices by means of combining different material witheach other. WO 2018/181188 describes the combination of a TADF materialwith another compound that has a lower first singlet state S1 than theTADF material. WO 2018/186404 describes the use of a dopant and twofurther compounds selected from a large list of compounds with differentstructural properties in layers. These prior art documents, however, donot teach optimized combinations of photoactive materials combined in asingle emitting layer.

WO 2015/135624 teaches an OLED which comprises a TADF material incombination with a sterically shielded fluorescent compound. WO2015/135624 does neither teach beneficial relations between singletenergy states of different optically active materials nor thecombination of specific types of emitter materials with other opticallyactive materials such as triplet-triplet annihilation materials. Thespecific examples disclosed in WO 2015/135624 as shown in Table 2thereof refer to materials having less beneficial optical propertiessuch as emission maxima at longer wavelengths in the green or yellowrange of the spectrum (emission maximum at >500 nm) and TADF materialsbearing singlet energy levels below that of the other optically activematerials.

There is still a need for efficient and stable OLEDs that emit in theblue region of the visible light spectrum, which would be expressed by asmall CIEy value. Accordingly, there is still the unmet technical needfor organic electroluminescent devices which have a long lifetime, inparticular in the blue range.

An interesting parameter is the onset of the emission of the emitterexpressed by the S1 energy. High energy photons, particularly incombination with further polarons or excited states, may lead todegradation of the organic materials, if the bond dissociation energy(BDE) of the weakest bond is exceeded. As a consequence, the S1 energyof the emitter contributing the main component of the emission should beas low as possible and thus an emitter with a small FWHM needs to beemployed for blue emissive OLEDs. In addition, other materials—such asthe host materials—should not contribute to the emission, as the S1energy of the host needs to be even higher in energy than the one of theemitters to avoid quenching. Consequently, an efficient energy transferfrom all materials within the emission layer to the emitter material isrequired.

Within the organic electroluminescent device comprising thetriplet-triplet annihilation material, the TADF material and the NRCTemitter material, an effective extension of the lifetime of the organicelectroluminescent device is achieved.

Surprisingly, it has been found that an organic electroluminescentdevice's light-emitting layer comprising a triplet-triplet annihilationmaterial, a thermally activated delayed fluorescence (TADF) material anda near-range charge transfer NRCT emitter material, which exhibits anarrow—expressed by a small full width at half maximum (FWHM)—blueemission, provides an organic electroluminescent device having goodlifetime and quantum yields and exhibiting blue emission. Herein, themain emission of the device occurs from the near-range charge transfer(NRCT) emitter. The combination of thermally activated fluorescence andtriplet-triplet annihilation bears unexpected technical advantages ashas been shown experimentally.

Surprisingly, energy transfer within the device is neverthelesssufficient enough to yield a blue emission with small FWHM and thus alow CIEy color coordinate.

Accordingly, one aspect of the present invention relates an organicelectroluminescent device comprising a light-emitting layer Bcomprising:

-   (i) a triplet-triplet annihilation (TTA) material H^(N), which has a    lowermost excited singlet state energy level S1^(N), a lowermost    excited triplet state energy level T1^(N),-   (ii) a thermally activated delayed fluorescence (TADF) material    E^(B), which has a lowermost excited singlet state energy level    S1^(E) and a lowermost excited triplet state energy level T1^(E);    and-   (iii) an organic near-range-charge-transfer (NRCT) emitter S^(B),    which has a lowermost excited singlet state energy level S1^(S) and    a lowermost excited triplet state energy level T1^(S),    wherein the relations expressed by the following formulas (1) to (3)    apply:

S1^(E) >S1^(S)  (1)

S1^(N) >S1^(S)  (2)

S1^(S)<2.95 eV  (3).

According to the invention, the lowermost excited singlet state of theTADF material E^(B) is higher in energy than the lowermost excitedsinglet state of S^(B).

The lowermost excited singlet state of the host material H^(N) is higherin energy than the organic near-range-charge-transfer (NRCT) emitterS^(B).

In one embodiment, the lowermost excited singlet state of the hostmaterial H^(N) is higher in energy than the lowermost excited singletstate of the TADF material E^(B).

The lowermost excited singlet state of S^(B), i.e. the onset of theemission spectrum of S^(B), is smaller than 2.95 eV, preferably smallerthan 2.90 eV, more preferably smaller than 2.85 eV, even more preferablysmaller than 2.80 eV or even smaller than 2.75 eV.

Surprisingly it was found, that the main contribution to the emissionband of the optoelectronic device according to the invention can beattributed to the emission of S^(B) indicating a sufficient transfer ofenergy transfer from E^(B) to S^(B) and from the triplet-tripletannihilation material H^(N) to E^(B) and/or S^(B).

FIG. 1 shows an example of the relation between the energy levels of theTADF material, the NRCT emitter and the TTA material. S0 represents theground state. The curved arrow at the TADF material illustrates thereversed intersystem crossing (RISC) from the lowermost excited tripletstate energy level T1^(E) of the TADF material to the lowermost excitedsinglet state energy level S1^(E) of the TADF material.

The curved arrow at the TTA material illustrates the triplet-tripletannihilation from the lowermost excited triplet state energy levelT1^(N) of the TTA material to the lowermost excited singlet state energylevel S1^(N) of the TTA material.

The dashed arrow at the NRCT emitter illustrates the emission from thelowermost excited singlet state energy level S1^(S).

Solid lines illustrate energy transfer processes between differentlowermost excited singlet states S1. In detail, an energy transfer fromS1^(N) to either S1^(E) or S1^(S), and the energy transfer from S1^(E)to S1^(S).

In one embodiment of the invention, the TADF material, the NRCT emitterand the TTA material are combined in a single light emitting layer B.Therefore, in the light emitting layer B, the TADF material, the NRCTemitter and the TTA material are preferably distributed in an(essentially) randomized mixture. In other words, the TADF material, theNRCT emitter and the TTA material do preferably not form distinguishablelayers. In one embodiment of the invention, the TADF material, the NRCTemitter and the TTA material are admixed with each other in a singlelight emitting layer B. In one embodiment of the invention, the lightemitting layer B is obtained from a mixture or co-deposition of the TADFmaterial, the NRCT emitter and the TTA material and optional one or morefurther materials.

In one embodiment of the invention, twice the energy of the lowermostexcited triplet state energy level T1^(N) of the TTA material is largerthan the energy of the lowermost excited singlet state energy levelS1^(S) of the NRCT emitter, i.e., 2×T1^(N)>S1^(S).

In one embodiment of the invention, the energy difference between thelowermost excited singlet state energy level S1^(E) of the TADF materialand the lowermost excited singlet state energy level S1^(S) of the NRCTemitter fulfills the relation:

0.0 eV≤S1^(E)−S1^(S)≤0.4 eV, preferably 0.0 eV≤S1^(E)−S1^(S)≤0.3 eV.

In one embodiment of the invention, the absolute value of the differencebetween the lowermost excited triplet state energy level T1^(E) of theTADF material and the lowermost excited singlet state energy levelS1^(S) of the NRCT emitter fulfills the relation: T1^(E)>S1^(S). In oneembodiment of the invention, the absolute value of the differencebetween the lowermost excited triplet state energy level T1^(E) of theTADF material and the lowermost excited singlet state energy levelS1^(S) of the NRCT emitter fulfills the relation: 0.0eV≤|T1^(E)−S1^(S)|≤0.3 eV

In one embodiment of the invention, the absolute value of the differencebetween the lowermost excited triplet state energy level T1^(E) of theTADF material and the lowermost excited triplet state energy levelT1^(S) of the NRCT emitter fulfills the relation: T1^(E)>T1^(S). In oneembodiment of the invention, the absolute value of the differencebetween the lowermost excited triplet state energy level T1^(E) of theTADF material and the lowermost excited triplet state energy levelT1^(S) of the NRCT emitter fulfills the relation: 0.0eV≤|T1^(E)−T1^(S)|≤0.5 eV

In one embodiment of the invention, the energy of the lowermost excitedtriplet state energy level T1^(E) of the TADF material is larger thanthe energy of the lowermost excited triplet state energy level T1^(N) ofthe TTA material, i.e., T1^(E)>T1^(N).

In one embodiment of the invention, the energy of the lowermost excitedtriplet state energy level T1^(S) of the NRCT emitter is larger than theenergy of the lowermost excited triplet state energy level T1^(N) of theTTA material, i.e., T1^(S)>T1^(N).

In one embodiment of the invention, the energy of the lowermost excitedtriplet state energy level T1^(E) of the TADF material is larger thanthe energy of the lowermost excited triplet state energy level T1^(S) ofthe NRCT emitter, i.e., T1^(E)>T1^(S).

In one embodiment of the invention, the difference between the lowermostexcited singlet state energy level S1^(N) of the TTA material and thelowermost excited singlet state energy level S1^(S) of the NRCT emitterfulfills the relation: 0.0 eV≤S1^(N)−S1^(S)≤0.8 eV.

In one embodiment of the invention, the difference between the lowermostexcited singlet state energy level S1^(N) of the TTA material and thelowermost excited singlet state energy level S1^(S) of the NRCT emitterfulfills the relation: 0.0 eV≤S1^(N)−S1^(S)≤0.4 eV.

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited singletstate energy level S1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>S1^(E)>S1^(S).

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited singletstate energy level S1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>S1^(E)>S1^(S), wherein

0.0 eV≤S1^(N) −S1^(S)≤0.8 eV.

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited singletstate energy level S1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>S1^(E)>S1^(S), wherein

0.0 eV≤S1^(N) −S1^(S)≤0.4 eV.

In one embodiment of the invention, T1^(E)>S1^(S).

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited tripletstate energy level T1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>T1^(E)>S1^(S).

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited tripletstate energy level T1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>T1^(E)>S1^(S), wherein

0.0 eV≤S1^(N) −S1^(S)≤0.8 eV.

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited tripletstate energy level T1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>T1^(E)>S1^(S), wherein

0.0 eV≤S1^(N) −S1^(S)≤0.4 eV.

In one embodiment of the invention, the lowermost excited singlet stateenergy level S1^(N) of the TTA material, the lowermost excited tripletstate energy level T1^(E) of the TADF material, and the lowermostexcited singlet state energy level S1^(S) of the NRCT emitter fulfillthe relation: S1^(N)>T1^(E)>S1^(S), wherein

0.0 eV≤S1^(N) −S1^(S)≤0.4 eV, and 0.0 eV≤|T1^(E) −S1^(S)≤0.3 eV.

In one embodiment of the invention, T1^(E)>T1^(N). In one embodiment ofthe invention, S1^(S)>T1^(N). In one embodiment of the invention,T1^(S)>T1^(N). In one embodiment of the invention, T1^(E)>T1^(S)>T1^(N).

In one embodiment of the invention,S1^(N)>S1^(E)>T1^(E)>S1^(S)>T1^(S)>T1^(N).

In one embodiment of the invention, the energetic difference betweenS1^(E) and T1^(E) (Δ(S1^(E)−T1^(E)), ΔE_(ST) value (E)) is smaller thanthe energetic difference between S1^(N) and T1^(N) (Δ(S1^(N)−T1^(N)),ΔE_(ST) value (N)). In one embodiment of the invention, Δ(S1^(N)−T1^(N))is at least 1.5 fold, at least 2 fold, at least 3 fold, at least 4 foldor at least 5 fold larger than Δ(S1^(E)−T1^(E)).

In one embodiment of the invention, the energetic difference betweenS1^(S) and T1^(S) (Δ(S1^(S)−T1^(S)), ΔE_(ST) value (S)) is smaller thanΔ(S1^(N)−T1^(N)). In one embodiment of the invention, Δ(S1^(N)−T1^(N))is at least 1.5 fold, at least 2 fold, at least 3 fold, at least 4 foldor at least 5 fold larger than Δ(S1^(S)−T1^(S)).

In one embodiment of the invention, Δ(S1^(E)−T1^(E))<Δ(S1^(S)−T1^(S)).

In one embodiment of the invention,Δ(S1^(E)−T1^(E))<Δ(S1^(S)−T1^(S))<Δ(S1^(N)−T1^(N)).

In one embodiment of the invention,Δ(S1^(E)−T1^(E))<Δ(S1^(S)−T1^(S))<Δ(S1^(N)−T1^(N)), wherein Δ(S1^(N)−T1^(N)) is at least 1.5 fold, at least 2 fold, at least 3 fold,at least 4 fold or at least 5 fold larger than Δ(S1^(S)−T1^(S)).

In a preferred embodiment, S1^(N) is in the range of from 1 to 5 eV,from 1.2 to 4 eV, from 1.4 to 3.8 eV, from 1.4 to 1.8 eV, from 1.6 to2.0 eV, from 1.8 to 2.2 eV, from 2.0 to 2.5 eV, from 2.0 to 3.5 eV, from2.5 to 3.5 eV, or from 2.8 to 4.0 eV. In a preferred embodiment, S1^(N)is in the range of from 3.0 to 3.5 eV or from 3.1 to 3.2 eV.

In a preferred embodiment, the emission of the organicelectroluminescent device mainly occurs from the NRCT emitter. In otherwords, the TTA material and/or the TADF material preferably transferenergy to the NRCT emitter and the NRCT emitter emits light.

The triplet-triplet annihilation (TTA) material H^(N) has a highestoccupied molecular orbital HOMO(H^(N)) having an energy E^(HOMO)(H^(N))and a lowest unoccupied molecular orbital LUMO(H^(N)) having an energyE^(LUMO)(H^(N)).

The TTA material enables triplet-triplet annihilation. Triplet-tripletannihilation may preferably result in a photon upconversion.Accordingly, two, three or even more photons may facilitate photonupconversion from the lowermost excited triplet state (T1^(N)) to thefirst excited singlet state S1^(N) of the TTA material H^(N). In apreferred embodiment, two photons facilitate photon upconversion fromT1^(N) to S1^(N). Triplet-triplet annihilation may thus be a processthat through a number of energy transfer steps, may combine two (oroptionally more than two) low frequency photons into one photon ofhigher frequency.

Optionally, the TTA material may comprise an absorbing moiety, thesensitizer moiety, and an emitting moiety (or annihilator moiety). Inthis context, an emitter moiety may, for example, be a polycyclicaromatic moiety such as, benzene, biphenyl, triphenyl, triphenylene,naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene,chrysene, perylene, azulene. In a preferred embodiment, the polycyclicaromatic moiety comprises an anthracene moiety or a derivative thereof.A sensitizer moiety and an emitting moiety may be located in twodifferent chemical compounds (i.e., separated chemical entities) or maybe both moieties embraced by one chemical compound.

In a preferred embodiment, the TTA material of the present invention atleast comprises or is the TTA emitter moiety. The TTA material mayoptionally, but not necessarily, also comprise the sensitizermoiety—either also two separate chemical compounds or combined with eachother in a single compound. When the TTA material does not comprise thesensitizer moiety, another compound present in the electroluminescentdevice may provide such properties.

The thermally activated delayed fluorescence (TADF) material E^(B) has ahighest occupied molecular orbital HOMO(E^(B)) having an energyE^(HOMO)(E^(B)) and a lowest unoccupied molecular orbital LUMO(E^(B))having an energy E^(LUMO)(E^(B)).

In one embodiment of the invention, the lowest unoccupied molecularorbital LUMO(E^(B)) of the TADF material, having an energyE^(LUMO)(E^(B)), and the lowest unoccupied molecular orbital LUMO(H^(N))of the TTA material, having an energy E^(LUMO)(H^(N)), fulfill therelation:

E ^(LUMO)(E ^(B))<E ^(LUMO)(H ^(N))

In one embodiment of the invention, the highest occupied molecularorbital HOMO(H^(N)) of the TTA material, having an energyE^(HOMO)(H^(N)), and the highest occupied molecular orbital HOMO(E^(B))of the TADF material having an energy E^(HOMO)(E^(B)), fulfill therelation:

E ^(HOMO)(H ^(N))>E ^(HOMO)(E ^(B))

According to the invention, a triplet-triplet annihilation (TTA)material may convert energy from first excited triplet states T1^(N) tofirst excited singlet states S1^(N) by triplet-triplet annihilation.

According to the present invention, a TTA material is characterized inthat it exhibits triplet-triplet annihilation from the lowermost excitedtriplet state (T1^(N)) resulting in a triplet-triplet annihilated firstexcited singlet state S1^(N), having an energy of up to two times theenergy of T1^(N).

In one embodiment of the present invention, a TTA material may becharacterized in that it exhibits triplet-triplet annihilation fromT1^(N) resulting in S1^(N), having an energy of 1.01 to 2 fold, 1.1 to1.9 fold, 1.2 to 1.5 fold, 1.4 to 1.6 fold, or 1.5 to 2 fold times theenergy of T1^(N).

As used herein, the terms “TTA material” and “TTA compound” may beunderstood interchangeably.

Typical “TTA material” can be found in the state of the art related toblue fluorescent OLEDs, as described by Kondakov (PhilosophicalTransactions of the Royal Society A: Mathematical, Physical andEngineering Sciences, 2015, 373:20140321). Such blue fluorescent OLEDsemploy aromatic hydrocarbons such as anthracene derivatives as the maincomponent (host) in the EML.

In a preferred embodiment, the TTA material enables sensitizedtriplet-triplet annihilation. Optionally, the TTA material may compriseone or more polycyclic aromatic structures. In a preferred embodiment,the TTA material comprises at least one polycyclic aromatic structureand at least one further aromatic residue.

In a preferred embodiment, the TTA material bears larger singlet-tripletenergy splitting, i.e., an energy difference between its first excitedsinglet state S1^(N) and its lowermost excited triplet state T1^(N) ofat least 1.1 fold, at least 1.2 fold, at least 1.3 fold, at least 1.5fold and preferably not more than 2 fold.

In a preferred embodiment of the invention, H^(N) is an anthracenederivative.

In one embodiment, H^(N) is an anthracene derivate as described in WO2018/186404 (in particular pages 71 to 95 thereof).

In one embodiment, H^(N) is an anthracene derivate of the followingformula (4)

wherein

each Ar is independently from each other selected from the groupconsisting of C₆-C₆₀-aryl, which is optionally substituted with one ormore residues selected from the group consisting of C₆-C₆₀-aryl,C₃-C₅₇-heteroaryl, halogen, and C₁-C₄₀-(hetero)alkyl;

and C₃-C₅₇-heteroaryl, which is optionally substituted with one or moreresidues selected from the group consisting of C₆-C₆₀-aryl,C₃-C₅₇-heteroaryl, halogen, and C₁-C₄₀-(hetero)alkyl; and

each A1 is independently from each other selected from the groupconsisting of consisting of

hydrogen;

deuterium;

C₆-C₆₀-aryl, which is optionally substituted with one or more residuesselected from the group consisting of C₆-C₆₀-aryl, C₃-C₅₇-heteroaryl,halogen, and C₁-C₄₀-(hetero)alkyl; C₃-C₅₇-heteroaryl, which isoptionally substituted with one or more residues selected from the groupconsisting of C₆-C₆₀-aryl, C₃-C₅₇-heteroaryl, halogen, andC₁-C₄₀-(hetero)alkyl; and

C₁-C₄₀-(hetero)alkyl, which is optionally substituted with one or moreresidues selected from the group consisting of C₆-C₆₀-aryl,C₃-C₅₇-heteroaryl, halogen, and C₁-C₄₀-(hetero)alkyl.

In one embodiment, H^(N) is an anthracene derivate of the followingformula (4), wherein

each Ar is independently from each other selected from the groupconsisting of C₆-C₂₀-aryl, which is optionally substituted with one ormore residues selected from the group consisting of C₆-C₂₀-aryl,C₃-C₂₀-heteroaryl, halogen, and C₁-C₂₁₀-(hetero)alkyl;

and C₃-C₂₀-heteroaryl, which is optionally substituted with one or moreresidues selected from the group consisting of C₆-C₂₀-aryl,C₃-C₂₀-heteroaryl, halogen, and C₁-C₁-(hetero)alkyl; and

each A₁ is independently from each other selected from the groupconsisting of consisting of

hydrogen,

deuterium,

C₆-C₂₀-aryl, which is optionally substituted with one or more residuesselected from the group consisting of C₆-C₂₀-aryl, C₃-C₂₀-heteroaryl,halogen, and C₁-C₁₀-(hetero)alkyl,

C₃-C₂₀-heteroaryl, which is optionally substituted with one or moreresidues selected from the group consisting of C₆-C₂₀-aryl,C₃-C₂₀-heteroaryl, halogen, and C₁-C₁₀-(hetero)alkyl; and

C₁-C₁₀-(hetero)alkyl, which is optionally substituted with one or moreresidues selected from the group consisting of C₆-C₆₀-aryl,C₃-C₅₇-heteroaryl, halogen, and C₁-C₄₀-(hetero)alkyl.

In one embodiment, H^(N) is an anthracene derivate of the followingformula (4), wherein at least one of A₁ is hydrogen. In one embodiment,H^(N) is an anthracene derivate of the following formula (4), wherein atleast two of A₁ are hydrogen. In one embodiment, H^(N) is an anthracenederivate of the following formula (4), wherein at least three of A₁ arehydrogen. In one embodiment, H^(N) is an anthracene derivate of thefollowing formula (4), wherein all of A₁ are each hydrogen.

In one embodiment, H^(N) is an anthracene derivate of the followingformula (4), wherein one of Ar is a residue selected from the groupconsisting of phenyl, naphthyl, phenanthryl, pyrenyl, triphenylenyl,dibenzoanthracenyl, fluorenyl, benzofluorenyl, anthracenyl,phenanthrenyl, benzonaphtofuranyl, benzonaphtothiopehnyl,dibenzofuranyl, dibenzothiopehnyl,

which may be each optionally substituted with one or more residuesselected from the group consisting of C₆-C₆₀-aryl, C₃-C₅₇-heteroaryl,halogen, and C₁-C₄₀-(hetero)alkyl.

In one embodiment, H^(N) is an anthracene derivate of the followingformula (4), wherein both Ar are residues each independently from eachother selected from the group consisting of phenyl, naphthyl,phenanthryl, pyrenyl, triphenylenyl, dibenzoanthracenyl, fluorenyl,benzofluorenyl, anthracenyl, phenanthrenyl, benzonaphtofuranyl,benzonaphtothiopehnyl, dibenzofuranyl, dibenzothiopehnyl,

which may be each optionally substituted with one or more residuesselected from the group consisting of C₆-C₆₀-aryl, C₃-C₅₇-heteroaryl,halogen, and C₁-C₄₀-(hetero)alkyl.

In one embodiment, H^(N) is an anthracene derivate selected from thefollowing:

As used herein, the terms “TADF material” and “TADF emitter” may beunderstood interchangeably.

The concept of TADF is described in the state of the art. As an example,TADF, TADF emitter, in particular blue TADF emitter and blue TADFemitter, are described by Zysman-Colman et al. (Advance Materials, 2017,29(22): 1605444, DOI: 10.1002/adma.201605444).

According to the present invention, a TADF material is characterized inthat it exhibits a ΔE_(ST) value, which corresponds to the energydifference between the lowermost excited singlet state (S1) and thelowermost excited triplet state (T1), of less than 0.4 eV, preferablyless than 0.3 eV, more preferably less than 0.2 eV, even more preferablyless than 0.1 eV or even less than 0.05 eV.

As used herein, the terms organic electroluminescent device andoptoelectronic light-emitting devices may be understood in the broadestsense as any device comprising a light-emitting layer B comprising, aTTA material, a TADF material E^(B) and a NRCT emitter S^(B).

As used herein, the terms “NRCT material” and “NRCT emitter” may beunderstood interchangeably.

The organic electroluminescent device may be understood in the broadestsense as any device based on organic materials that is suitable foremitting light in the visible or nearest ultraviolet (UV) range, i.e.,in the range of a wavelength of from 380 to 800 nm. More preferably,organic electroluminescent device may be able to emit light in thevisible range, i.e., of from 400 to 800 nm.

The NRCT emitter S^(B) is chosen to exhibit an emission with a fullwidth at half maximum (FWHM) below 0.35 eV, preferably less than 0.30eV, more preferably less than 0.25 eV, even more preferably less than0.20 or even less than 0.15 eV in PMMA with 5% by weight of the NRCTemitter S^(B).

In a preferred embodiment, the TADF material E^(B) exhibits a ΔE_(ST)value, which corresponds to the energy difference between the lowermostexcited singlet state (S1) and the lowermost excited triplet state (T1),of less than 0.4 eV; and

the NRCT emitter S^(B) exhibits an emission with a full width at halfmaximum (FWHM) below 0.35 eV, in PMMA with 5% by weight of the NRCTemitter S^(B).

In a preferred embodiment, the organic electroluminescent device is adevice selected from the group consisting of an organic light emittingdiode (OLED), a light emitting electrochemical cell (LEC), and alight-emitting transistor.

Particularly preferably, the organic electroluminescent device is anorganic light emitting diode (OLED). Optionally, the organicelectroluminescent device as a whole may be intransparent,semi-transparent or (essentially) transparent.

The term “layer” as used in the context of the present inventionpreferably is a body that bears an extensively planar geometry. Thelight-emitting layer B preferably bears a thickness of not more than 1mm, more preferably not more than 0.1 mm, even more preferably not morethan 10 μm, even more preferably not more than 1 μm, in particular notmore than 0.1 μm.

In a preferred embodiment, the thermally activated delayed fluorescence(TADF) material E^(B) is an organic TADF material. According to theinvention, organic emitter or organic material means that the emitter ormaterial (predominantly) consists of the elements hydrogen (H), carbon(C), nitrogen (N), boron (B), silicon (Si) and optionally fluorine (F),optionally bromine (Br) and optionally oxygen (O). Particularlypreferably, it does not contain any transition metals.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial. In a preferred embodiment, the small FWHM emitter S^(B) is anorganic emitter. In a more preferred embodiment, the TADF material E^(B)and the small FWHM emitter S^(B) are both organic materials.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial, which is chosen from molecules of a structure of FormulaI-TADF

wherein

n is at each occurrence independently from another 1 or 2;

X is at each occurrence independently from another selected Ar^(EWG), CNor CF₃;

Z is at each occurrence independently from another selected from thegroup consisting of a direct bond, CR³R⁴, C═CR³R⁴, C═O, C═NR³, NR³, O,SiR³R⁴, S, S(O) and S(O)₂;

Ar^(EWG) is at each occurrence independently from another a structureaccording to one of Formulas IIa to IIk

wherein # represents the binding site of the single bond linkingAr^(EWG) to the substituted central phenyl ring of Formula I-TADF;

R¹ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one ormore hydrogen atoms are optionally substituted by deuterium, andC₆-C₁₈-aryl, which is optionally substituted with one or moresubstituents R⁶;

R² is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one ormore hydrogen atoms are optionally substituted by deuterium, andC₆-C₁₈-aryl, which is optionally substituted with one or moresubstituents R⁶;

R^(a), R³ and R⁴ is at each occurrence independently from anotherselected from the group consisting of hydrogen, deuterium, N(R⁵)₂, OR⁵,

SR⁵, Si(R⁵)₃, CF₃, CN, F,

C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;

C₁-C₄₀-thioalkoxy which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; and

C₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵;

R⁵ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, N(R⁶)₂, OR⁶, SR⁶, Si(R⁶)₃, CF₃,CN, F,

C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁶ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁶C═CR⁶, C≡C, Si(R⁶)₂, Ge(R⁶)₂, Sn(R⁶)₂, C═O,C═S, C═Se, C═NR⁶, P(═O)(R⁶), SO, SO₂, NR⁶, O, S or CONR⁶;

C₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁶; and

C₃-C₅₇-heteroaryl which is optionally substituted with one or moresubstituents R⁶;

R⁶ is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, OPh, CF₃, CN, F,

C₁-C₅-alkyl, wherein one or more hydrogen atoms are optionally,independently from each other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-alkoxy,

wherein one or more hydrogen atoms are optionally, independently fromeach other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-thioalkoxy, wherein one or more hydrogen atoms are optionally,independently from each other substituted by deuterium, CN, CF₃, or F;

C₆-C₁₈-aryl which is optionally substituted with one or more C₁-C₅-alkylsubstituents;

C₃-C₁₇-heteroaryl which is optionally substituted with one or moreC₁-C₅-alkyl substituents;

N(C₆-C₁₈-aryl)₂;

N(C₃-C₁₇-heteroaryl)₂, and

N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl);

R^(d) is at each occurrence independently from another selected from thegroup consisting of hydrogen, deuterium, N(R⁵)₂, OR⁵,

SR⁵, Si(R⁵)₃, CF₃, CN, F,

C₁-C₄₀-alkyl which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;

C₁-C₄₀-thioalkoxy which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; and

C₆-C₆₀-aryl which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵;

wherein the substituents R^(a), R³, R⁴ or R⁵ independently from eachother optionally may form a mono- or polycyclic, aliphatic, aromaticand/or benzo-fused ring system with one or more substituents R^(a), R³,R⁴ or R⁵ and

wherein the one or more substituents R^(d) independently from each otheroptionally may form a mono- or polycyclic, aliphatic, aromatic and/orbenzo-fused ring system with one or more substituents R^(d).

According to the invention, the substituents R^(a), R³, R⁴ or R⁵ at eachoccurrence independently from each other may optionally form a mono- orpolycyclic, aliphatic, aromatic and/or benzo-fused ring system with oneor more substituents R^(a), R³, R⁴ or R⁵.

According to the invention, the substituents R^(d) at each occurrenceindependently from each other may optionally form a mono- or polycyclic,aliphatic, aromatic and/or benzo-fused ring system with one or moreother substituents R^(d).

In a particularly preferred embodiment of the invention, Z is a directbond at each occurrence.

In one embodiment of the invention, the TADF material E^(B) comprises atleast one triazine structure according to Formula IIa.

In a preferred embodiment, the TADF material E^(B) is an organic TADFmaterial, which is chosen from molecules of a structure of FormulaII-TADF

In one embodiment of the invention, R^(a) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph; and N(Ph)₂.

In one embodiment of the invention, R^(d) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃ and Ph;

triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃ and Ph; and N(Ph)₂.

In a preferred embodiment, X is CN.

In one embodiment of the invention, the TADF material E^(B) is chosenfrom a structure of Formula III:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIa:

wherein R^(a), X and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIIc:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IIId:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IV:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IVa:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IVb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula V:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Va:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Vb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VI:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIa:

wherein R^(a), R¹ and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIb:

wherein R^(a) and R¹ are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VII:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIII:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula VIIIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IX:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IXa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula IXb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula X:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Xa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula Xb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XI:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIa:

wherein R^(a) and X are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIb:

wherein R^(a) is defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XII:

wherein R^(a), X and R^(d) are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIIa:

wherein R^(a), X and R^(d) are defined as above.

In one embodiment of the invention, E^(B) is chosen from molecules of astructure of Formula XIIb:

wherein R^(a), X and R^(d) are defined as above.

The synthesis of the molecules of a structure of Formula I-TADF can beaccomplished via standard reactions and reaction conditions known to theskilled artesian. Typically, in a first step a coupling reaction,preferably a palladium catalyzed coupling reaction, is performed.

E1 can be any boronic acid (R^(B)═H) or an equivalent boronic acid ester(R^(B)=alkyl or aryl), in particular two R^(B) form a ring to give e.g.boronic acid pinacol esters, of fluoro-(trifluoromethyl)phenyl,difluoro-(trifluoromethyl)phenyl, fluoro-(cyano)phenyl ordifluoro-(cyano)phenyl. As second reactant E2 preferably Ar^(EWG)—Br isused. Reaction conditions of such palladium catalyzed coupling reactionsare known the person skilled in the art, e.g. from WO 2017/005699, andit is known that the reacting groups of E1 and E2 can be interchanged tooptimize the reaction yields.

In a second step, the molecules according to Formula I-TADF are obtainedvia the reaction of a nitrogen heterocycle in a nucleophilic aromaticsubstitution with the aryl halide, preferably aryl fluoride, or aryldihalide, preferably aryl difluoride, E3. Typical conditions include theuse of a base, such as tribasic potassium phosphate or sodium hydride,for example, in an aprotic polar solvent, such as dimethyl sulfoxide(DMSO) or N,N-dimethylformamide (DMF), for example.

particular, the donor molecule E6 is a 3,6-substituted carbazole (e.g.,3,6-dimethylcarbazole, 3,6 diphenylcarbazole,3,6-di-tert-butylcarbazole), a 2,7-substituted carbazole (e.g., 2,7dimethylcarbazole, 2,7-diphenylcarbazole, 2,7-di-tert-butylcarbazole), a1,8-substituted carbazole (e.g., 1,8-dimethylcarbazole,1,8-diphenylcarbazole, 1,8-di-tert-butylcarbazole), a 1 substitutedcarbazole (e.g., 1-methylcarbazole, 1-phenylcarbazole,1-tert-butylcarbazole), a 2 substituted carbazole (e.g.,2-methylcarbazole, 2-phenylcarbazole, 2-tert-butylcarbazole), or a 3substituted carbazole (e.g., 3-methylcarbazole, 3-phenylcarbazole,3-tert-butylcarbazole).

Alternatively, a halogen-substituted carbazole, particularly3-bromocarbazole, can be used as E6.

In a subsequent reaction a boronic acid ester functional group orboronic acid functional group may be exemplarily introduced at theposition of the one or more halogen substituents, which was introducedvia E6, to yield the corresponding carbazol-3-ylboronic acid ester orcarbazol-3-ylboronic acid, e.g., via the reaction withbis(pinacolato)diboron (CAS No. 73183-34-3). Subsequently, one or moresubstituents R^(a) may be introduced in place of the boronic acid estergroup or the boronic acid group via a coupling reaction with thecorresponding halogenated reactant R^(a)-Hal, preferably R^(a)—Cl andR^(a)—Br. Alternatively, one or more substituents R^(a) may beintroduced at the position of the one or more halogen substituents,which was introduced via D-H, via the reaction with a boronic acid ofthe substituent R^(a) [R^(a)—B(OH)₂] or a corresponding boronic acidester.

An alternative synthesis route comprises the introduction of a nitrogenheterocycle via copper- or palladium-catalyzed coupling to an arylhalide or aryl pseudohalide, preferably an aryl bromide, an aryl iodide,aryl triflate or an aryl tosylate.

As used throughout the present application, the terms “aryl” and“aromatic” may be understood in the broadest sense as any mono-, bi- orpolycyclic aromatic moieties. If not otherwise indicated, an aryl mayalso be optionally substituted by one or more substituents which areexemplified further throughout the present application. Accordingly, theterm “arylene” refers to a divalent residue that bears two binding sitesto other molecular structures and thereby serving as a linker structure.As used throughout the present application, the terms “heteroaryl” and“heteroaromatic” may be understood in the broadest sense as any mono-,bi- or polycyclic heteroaromatic moieties that include at least oneheteroatom, in particular which bear from one to three heteroatoms peraromatic ring.

Exemplarily, a heteroaromatic compound may be pyrrole, furan, thiophene,imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine andpyrimidine, and the like. If not otherwise indicated, a heteroaryl mayalso be optionally substituted by one or more substituents which areexemplified further throughout the present application. Accordingly, theterm “heteroarylene” refers to a divalent residue that bears two bindingsites to other molecular structures and thereby serving as a linkerstructure.

As used throughout the present application, the term “alkyl” may beunderstood in the broadest sense as both, linear or branched chain alkylresidue. Preferred alkyl residues are those containing from one tofifteen carbon atoms. Exemplarily, an alkyl residue may be methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the like. Ifnot otherwise indicated, an alkyl may also be optionally substituted byone or more substituents which are exemplified further throughout thepresent application. Accordingly, the term “alkylene” refers to adivalent residue that bears two binding sites to other molecularstructures and thereby serving as a linker structure.

If not otherwise indicated, as used herein, in particular in the contextof aryl, arylene, heteroaryl, alkyl and the like, the term “substituted”may be understood in the broadest sense. Preferably, such substitutionmeans a residue selected from the group consisting of C₁-C₂₀-alkyl,C₇-C₁₉-alkaryl, and C₆-C₁₈-aryl. Accordingly, preferably, no chargedmoiety, more preferably no functional group is present in suchsubstitution.

It will be noticed that hydrogen can, at each occurrence, be replaced bydeuterium.

In a particularly preferred embodiment, the at least one TADF materialE^(B) is a blue TADF material, preferably a deep-blue TADF material.

The compounds H^(N) and the emitters E^(B) and S^(B) may be comprised inthe organic electroluminescent device in any amount and any ratio.

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises morecompound H^(N) than emitter E^(B), according to the weight.

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises more TADFmaterial E^(B) than emitter S^(B), according to the weight.

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises 10-96.5% byweight, or 10-96% by weight, or 10-84% by weight, or 40-74% by weight,or 50 to 96.5% by weight of the TTA material H^(N).

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises 3-50% byweight, or 15-30% by weight, of the TADF material E^(B).

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B (optionally) comprises0.5-30% by weight, or 1-30% by weight, or 1-10% by weight, or 1-5% byweight, of the emitter S^(B).

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B (optionally) comprises0-74% by weight, or 0-34% by weight, or 0-25% by weight, or 0-10% byweight, or 0-5% by weight, of one or more solvents.

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises (or consistof):

-   (i) 10-96.5% by weight, preferably 10-96% by weight of the TTA    material H^(N);-   (ii) 3-50% by weight of the TADF material E^(B); and-   (iii) 0.5-30% by weight, preferably 1-30% by weight of the emitter    S^(B); and optionally-   (iv) 0-74% by weight of one or more solvents.

In a preferred embodiment, in the organic electroluminescent device ofthe present invention, the light-emitting layer B comprises (or consistof):

-   (i) 10-84% by weight of the TTA material H^(N);-   (ii) 3-50% by weight of the TADF material E^(B); and-   (iii) 1-30% by weight of the emitter S^(B); and optionally-   (iv) 0-74% by weight of one or more solvents.

In a preferred embodiment, the percentage numbers of (i)-(iv) sum up to100% by weight.

In another preferred embodiment, in the organic electroluminescentdevice of the present invention, the light-emitting layer B comprises(or consist of):

-   (i) 40-74% by weight of the TTA material H^(N);-   (ii) 15-30% by weight of the TADF material E^(B); and-   (iii) 1-5% by weight of the emitter S^(B); and optionally-   (iv) 0-34% by weight of one or more solvents.

In a preferred embodiment, the percentage numbers of (i)-(iv) sum up to100% by weight.

In a preferred embodiment, the TADF material E^(B) exhibits an emissionmaximum (determined in poly(methyl methacrylate) (PMMA), λ_(max)^(PMMA)(E^(B))) in the range from 440 to 470 nm. In a preferredembodiment, TADF material E^(B) exhibits an emission maximum λ_(max)^(PMMA)(E^(B)) in the range from 445 to 465 nm.

According to the invention, a NRCT emitter shows a delayed component inthe time-resolved photoluminescence spectrum and exhibits a near-rangeHOMO-LUMO separation as described by Hatakeyama et al. (AdvancedMaterials, 2016, 28(14):2777-2781, DOI: 10.1002/adma.201505491). In someembodiments, the NRCT emitter is a TADF material.

In one embodiment, the NRCT emitter S^(B) is a blue boron containingNRCT emitter.

In a preferred embodiment, the NRCT emitter S^(B) comprises or consistsof a polycyclic aromatic compound.

In a preferred embodiment, the NRCT emitter S^(B) comprises or consistsof a polycyclic aromatic compound according to formula (1) or (2) or aspecific example described in US-A 2015/236274. US-A 2015/236274 alsodescribes examples for synthesis of such compounds.

In one embodiment, the NRCT emitter S^(B) comprises or consists of astructure according to Formula I-NRCT:

wherein

o is 0 or 1.

m=1-o.

X¹ is N or B.

X² is N or B.

X³ is N or B.

W is selected from the group consisting of Si(R^(3S))₂, C(R^(3S))₂ andBR^(3S).

each of R^(1S), R^(2S) and R^(3S) is independently from each otherselected from the group consisting of:

C₁-C₅-alkyl, which is optionally substituted with one or moresubstituents R^(6S);

C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R^(6S); and

C₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R^(6S);

each of R^(I), R^(II), R^(III), R^(IV), R^(V), R^(VI), R^(VII),R^(VIII), R^(IX), R^(X), and R^(XI) is independently from anotherselected from the group consisting of: hydrogen, deuterium, N(R^(5S))₂,OR^(5S), Si(R^(5S))₃, B(OR^(5S))₂, OSO₂R^(5S), CF₃, CN, halogen,

C₁-C₄₀-alkyl, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S);

C₁-C₄₀-alkoxy, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S);

C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S);

C₂-C₄₀-alkenyl, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S);

C₂-C₄₀-alkynyl, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S);

C₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R^(5S); and

C₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R^(5S).

R^(5S) is at each occurrence independently from another selected fromthe group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,

C₁-C₅-alkyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-alkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-thioalkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₂-C₅-alkenyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₂-C₅-alkynyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;

C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;

N(C₆-C₁₈-aryl)₂,

N(C₃-C₁₇-heteroaryl)₂; and

N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).

R^(6S) is at each occurrence independently from another selected fromthe group consisting of hydrogen, deuterium, OPh, CF₃, CN, F,

C₁-C₅-alkyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-alkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₁-C₅-thioalkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₂-C₅-alkenyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₂-C₅-alkynyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;

C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;

C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents;

N(C₆-C₁₈-aryl)₂,

N(C₃-C₁₇-heteroaryl)₂; and

N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl).

According to a preferred embodiment, two or more of the substituentsselected from the group consisting of R^(I), R^(II), R^(III), R^(IV),R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) that arepositioned adjacent to another may each form a mono- or polycyclic,aliphatic, aromatic and/or benzo-fused ring system with another.

According to a preferred embodiment, at least one of X¹, X² and X³ is Band at least one of X¹, X² and X³ is N.

According to a preferred embodiment of the invention, at least onesubstituent selected from the group consisting of R^(I), R^(II),R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), andR^(XI) optionally forms a mono- or polycyclic, aliphatic, aromaticand/or benzo-fused ring system with one or more substituents of the samegroup that is/are positioned adjacent to the at least one substituent.

According to a preferred embodiment of the invention, at least one ofX¹, X² and X³ is B and at least one of X¹, X² and X³ is N.

In one embodiment, NRCT emitter S^(B) comprises or consists of astructure according to Formula 1 and X¹ and X³ each are N and X² is B:

In one embodiment, NRCT emitter S^(B) comprises or consists of astructure according to Formula 1 and X¹ and X³ each are B and X² is N:

In one embodiment, the small FWHM emitter S^(B) comprises or consists ofa structure according to Formula 1 and o=0.

In one embodiment, each of R^(1S) and R^(2S) is each independently fromeach other selected from the group consisting of

C₁-C₅-alkyl, which is optionally substituted with one or moresubstituents R^(6S);

C₆-C₃₀-aryl, which is optionally substituted with one or moresubstituents R^(6S); and

C₃-C₃₀-heteroaryl, which is optionally substituted with one or moresubstituents R^(6S).

In one embodiment, R^(1S) and R^(2S) is each independently from eachother selected from the group consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph; and

triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph.

In one embodiment, each of R^(I), R^(II), R^(III), R^(IV), R^(V),R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) is independentlyfrom another selected from the group consisting of: hydrogen, deuterium,halogen, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

and N(Ph)₂.

In one embodiment, each of R^(I), R^(II), R^(III), R^(IV), R^(V),R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) is independentlyfrom another selected from the group consisting of: hydrogen, deuterium,halogen, Me, ^(i)Pr, ^(t)Bu, CN, CF₃,

Ph, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyridinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

pyrimidinyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

carbazolyl, which is optionally substituted with one or moresubstituents independently from each other selected from the groupconsisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

triazinyl, which is optionally substituted with one or more substituentsindependently from each other selected from the group consisting of Me,^(i)Pr, ^(t)Bu, CN, CF₃, and Ph;

and N(Ph)₂; and

R^(1S) and R^(2S) is each independently from each other selected fromthe group consisting of

C₁-C₅-alkyl, which is optionally substituted with one or moresubstituents R^(6S);

C₆-C₃₀-aryl, which is optionally substituted with one or moresubstituents R^(6S); and

C₅-C₃₀-heteroaryl, which is optionally substituted with one or moresubstituents R^(6S).

In one embodiment, the NRCT emitter S^(B) is a blue boron-containingNRCT emitter selected from the following group:

In a preferred embodiment, the NRCT emitter S^(B) exhibits an emissionmaximum (determined in poly(methyl methacrylate) (PMMA), λ_(max)^(PMMA)(S^(B))) in the range from 440 to 475 nm. In a preferredembodiment, NRCT material S^(B) exhibits an emission maximum λ_(max)^(PMMA)(S^(B)) in the range from 445 to 465 nm.

The person skilled in the art will notice that the light-emitting layerB will typically be incorporated in the organic electroluminescentdevice of the present invention. Preferably, such organicelectroluminescent device comprises at least the following layers: atleast one light-emitting layer B, at least one anode layer A and atleast one cathode layer C.

Preferably, the anode layer A contains at least one component selectedfrom the group consisting of indium tin oxide, indium zinc oxide, PbO,SnO, graphite, doped silicium, doped germanium, doped GaAs, dopedpolyaniline, doped polypyrrole, doped polythiophene, and mixtures of twoor more thereof.

Preferably, the cathode layer C contains at least one component selectedfrom the group consisting of Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, In, W,Pd, LiF, Ca, Ba, Mg, and mixtures or alloys of two or more thereof.

Preferably, the light-emitting layer B is located between an anode layerA and a cathode layer C. Accordingly, the general set-up is preferablyA-B-C. This does of course not exclude the presence of one or moreoptional further layers. These can be present at each side of A, of Band/or of C.

In a preferred embodiment, the organic electroluminescent devicecomprises at least the following layers:

-   A) an anode layer A containing at least one component selected from    the group consisting of indium tin oxide, indium zinc oxide, PbO,    SnO, graphite, doped silicium, doped germanium, doped GaAs, doped    polyaniline, doped polypyrrole, doped polythiophene, and mixtures of    two or more thereof;-   B) the light-emitting layer B; and-   C) a cathode layer C containing at least one component selected from    the group consisting of Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, In, W,    Pd, LiF, Ca, Ba, Mg, and mixtures or alloys of two or more thereof,    wherein the light-emitting layer B is located between the anode    layer A and the a cathode layer C.

In one embodiment, when the organic electroluminescent device is anOLED, it may optionally comprise the following layer structure:

-   A) an anode layer A, exemplarily comprising indium tin oxide (ITO);-   HTL) a hole transport layer HTL;-   B) a light-emitting layer B according to present invention as    described herein;-   ETL) an electron transport layer ETL; and-   C) a cathode layer, exemplarily comprising Al, Ca and/or Mg.

Preferably, the order of the layers herein is A-HTL-B-ETL-C.

Furthermore, the organic electroluminescent device may optionallycomprise one or more protective layers protecting the device fromdamaging exposure to harmful species in the environment including,exemplarily moisture, vapor and/or gases.

Preferably, the anode layer A is located on the surface of a substrate.The substrate may be formed by any material or composition of materials.Most frequently, glass slides are used as substrates. Alternatively,thin metal layers (e.g., copper, gold, silver or aluminum films) orplastic films or slides may be used. This may allow a higher degree offlexibility. The anode layer A is mostly composed of materials allowingto obtain an (essentially) transparent film. As at least one of bothelectrodes should be (essentially) transparent in order to allow lightemission from the OLED, either the anode layer A or the cathode layer Ctransparent. Preferably, the anode layer A comprises a large content oreven consists of transparent conductive oxides (TCOs).

Such anode layer A may exemplarily comprise indium tin oxide, aluminumzinc oxide, fluor tin oxide, indium zinc oxide, PbO, SnO, zirconiumoxide, molybdenum oxide, vanadium oxide, wolfram oxide, graphite, dopedSi, doped Ge, doped GaAs, doped polyaniline, doped polypyrrol and/ordoped polythiophene.

Particularly preferably, the anode layer A (essentially) consists ofindium tin oxide (ITO) (e.g., (InO₃)_(0.9)(SnO₂)_(0.1)). The roughnessof the anode layer A caused by the transparent conductive oxides (TCOs)may be compensated by using a hole injection layer (HIL). Further, theHIL may facilitate the injection of quasi charge carriers (i.e., holes)in that the transport of the quasi charge carriers from the TCO to thehole transport layer (HTL) is facilitated. The hole injection layer(HIL) may comprise poly-3,4-ethylendioxy thiophene (PEDOT), polystyrenesulfonate (PSS), MoO₂, V₂O₅, CuPC or Cul, in particular a mixture ofPEDOT and PSS. The hole injection layer (HIL) may also prevent thediffusion of metals from the anode layer A into the hole transport layer(HTL). The HIL may exemplarily comprise PEDOT:PSS (poly-3,4-ethylendioxythiophene:polystyrene sulfonate), PEDOT (poly-3,4-ethylendioxythiophene), mMTDATA (4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine),Spiro-TAD (2,2′,7,7′-tetrakis(n,n-diphenylamino)-9,9′-spirobifluorene),DNTPD(N1,N1′-(biphenyl-4,4′-diyl)bis(N1-phenyl-N4,N4-di-m-tolylbenzene-1,4-diamine),NPB(N,N′-nis-(1-naphthalenyl)-N,N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine),NPNPB (N,N′-diphenyl-N,N′-di-[4-(N,N-diphenyl-amino)phenyl]benzidine),MeO-TPD (N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzi-dine), HAT-CN(1,4,5,8,9,11-hexaazatriphenylen-hexacarbonitrile) and/or Spiro-NPD(N,N′-diphenyl-N,N′-bis-(1-naphthyl)-9,9′-spirobifluorene-2,7-diamine).

Adjacent to the anode layer A or hole injection layer (HIL) typically ahole transport layer (HTL) is located. Herein, any hole transportcompound may be used. Exemplarily, electron-rich heteroaromaticcompounds such as triarylamines and/or carbazoles may be used as holetransport compound. The HTL may decrease the energy barrier between theanode layer A and the light-emitting layer B (serving as emitting layer(EML)). The hole transport layer (HTL) may also be an electron blockinglayer (EBL). Preferably, hole transport compounds bear comparably highenergy levels of their triplet states T1. Exemplarily the hole transportlayer (HTL) may comprise a star-shaped heterocycle such astris(4-carbazoyl-9-ylphenyl)amine (TCTA), poly-TPD(poly(4-butylphenyl-diphenyl-amine)), [alpha]-NPD(poly(4-butylphenyl-diphenyl-amine)), TAPC(4,4′-cyclohexyliden-bis[N,N-bis(4-methylphenyl)benzenamine]), 2-TNATA(4,4′,4″-tris[2-naphthyl(phenyl)-amino]triphenylamine), Spiro-TAD,DNTPD, NPB, NPNPB, MeO-TPD, HAT-CN and/or TrisPcz(9,9′-diphenyl-6-(9-phenyl-9H-carbazol-3-yl)-9H,9′H-3,3′-bicarbazole).In addition, the HTL may comprise a p-doped layer, which may be composedof an inorganic or organic dopant in an organic hole-transportingmatrix. Transition metal oxides such as vanadium oxide, molybdenum oxideor tungsten oxide may exemplarily be used as inorganic dopant.Tetrafluorotetracyanoquinodimethane (F4-TCNQ),copper-pentafluorobenzoate (Cu(I)pFBz) or transition metal complexes mayexemplarily be used as organic dopant.

The EBL may exemplarily comprise mCP (1,3-bis(carbazol-9-yl)benzene),TCTA, 2-TNATA, mCBP (3,3-di(9H-carbazol-9-yl)biphenyl),9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzofuran-2-yl)phenyl]-9H-carbazole,9-[3-(dibenzothiophen-2-yl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzofuranyl)phenyl]-9H-carbazole,9-[3,5-bis(2-dibenzothiophenyl)phenyl]-9H-carbazole, tris-Pcz, CzSi(9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole),3′,5′-di-(N-carbazolyl)-[1,1′-biphenyl]-2-carbonitrile (DCPBN; CAS1918991-70-4), 3-(N-carbazolyl)-N-phenylcarbazole (NCNPC) and/or DCB(N,N′-dicarbazolyl-1,4-dimethylbenzene).

Orbital and excited state energies can be determined by means ofexperimental methods known to the person skilled in the art.Experimentally, the energy of the highest occupied molecular orbitalE^(HOMO) is determined by methods known to the person skilled in the artfrom cyclic voltammetry measurements with an accuracy of 0.1 eV. Theenergy of the lowest unoccupied molecular orbital E^(LUMO) is calculatedas E^(HOMO)+E^(gap), where E^(gap) is determined as follows:

For TTA material compounds, the onset of emission of a neat film, whichcorresponds to the energy of the first excited singlet state S1, is usedas E^(gap), unless stated otherwise.

For TADF material compounds, the onset of emission of a film with 10% byweight of host in poly(methyl methacrylate) (PMMA), which corresponds tothe energy of the first excited singlet state S1, is used as E^(gap),unless stated otherwise.

For NRCT emitter compounds, the onset of emission of a film with 5% byweight of host in poly(methyl methacrylate) (PMMA), which corresponds tothe energy of the first excited singlet state S1, is used as E^(gap),unless stated otherwise.

For host compounds, the energy of the first excited triplet state T1 isdetermined from the onset of the time-gated emission spectrum at 77 K,typically with a delay time of 1 ms and an integration time of 1 ms, ifnot otherwise stated, measured in a film of poly(methyl methacrylate)(PMMA) with 10% by weight of host.

For TTA material compounds, the energy of the first excited tripletstate T1 is determined from the onset of the time-gated emissionspectrum at 77 K, typically with a delay time of 1 ms and an integrationtime of 1 ms, if not otherwise stated, measured in a neat film of theTTA material.

For TADF material compounds, the energy of the first excited tripletstate T1 is determined from the onset of the time-gated emissionspectrum at 77 K, typically with a delay time of 1 ms and an integrationtime of 1 ms, if not otherwise stated, measured in a film of poly(methylmethacrylate) (PMMA) with 10% by weight of TADF material.

For NRCT emitter compounds, the energy of the first excited tripletstate T1 is determined from the onset of the time-gated emissionspectrum at 77 K, typically with a delay time of 1 ms and an integrationtime of 1 ms, if not otherwise stated measured in a film of poly(methylmethacrylate) (PMMA) with 1% by weight of NRCT emitter.

In the electron transport layer (ETL), any electron transporter may beused. Exemplarily, compounds poor of electrons such as, e.g.,benzimidazoles, pyridines, triazoles, oxadiazoles (e.g.,1,3,4-oxadiazole), phosphinoxides and sulfone, may be used. Exemplarily,an electron transporter ETM may also be a star-shaped heterocycle suchas 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi). The ETMmay exemplarily be NBphen(2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), Alq3(Aluminum-tris(8-hydroxyquinoline)), TSPO1(diphenyl-4-triphenylsilylphenyl-phosphinoxide), BPyTP2(2,7-di(2,2′-bipyridin-5-yl)triphenyle), Sif87(dibenzo[b,d]thiophen-2-yltriphenylsilane), Sif88(dibenzo[b,d]thiophen-2-yl)diphenylsilane), BmPyPhB(1,3-bis[3,5-di(pyridin-3-yl)phenyl]benzene) and/or BTB(4,4′-bis-[2-(4,6-diphenyl-1,3,5-triazinyl)]-1,1′-biphenyl). Optionally,the electron transport layer may be doped with materials such as Liq(8-hydroxyquinolinolatolithium). Optionally, a second electron transportlayer may be located between electron transport layer and the cathodelayer C. The electron transport layer (ETL) may also block holes or ahole-blocking layer (HBL) is introduced.

The HBL may, for example, comprise BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline=Bathocuproine), BAIq(bis(8-hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum), NBphen(2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), Alq3(Aluminum-tris(8-hydroxyquinoline)), TSPO1(diphenyl-4-triphenylsilylphenyl-phosphinoxide), T2T(2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine), T3T(2,4,6-tris(triphenyl-3-yl)-1,3,5-triazine), TST(2,4,6-tris(9,9′-spirobifluorene-2-yl)-1,3,5-triazine), DTST(2,4-diphenyl-6-(3′-triphenylsilylphenyl)-1,3,5-triazine), DTDBF(2,8-bis(4,6-diphenyl-1,3,5-triazinyl)dibenzofurane) and/or TCB/TCP(1,3,5-tris(N-carbazolyl)benzol/1,3,5-tris(carbazol)-9-yl) benzene).

Adjacent to the electron transport layer (ETL), a cathode layer C may belocated. Exemplarily, the cathode layer C may comprise or may consist ofa metal (e.g., Al, Au, Ag, Pt, Cu, Zn, Ni, Fe, Pb, LiF, Ca, Ba, Mg, In,W, or Pd) or a metal alloy. For practical reasons, the cathode layer Cmay also consist of (essentially) intransparent metals such as Mg, Ca orAl. Alternatively or additionally, the cathode layer C may also comprisegraphite and or carbon nanotubes (CNTs). Alternatively, the cathodelayer C may also consist of nanoscale silver wires.

An OLED may further, optionally, comprise a protection layer between theelectron transport layer (ETL) D and the cathode layer C (which may bedesignated as electron injection layer (EIL)). This layer may compriselithium fluoride, caesium fluoride, silver, Liq(8-hydroxyquinolinolatolithium), Li₂O, BaF₂, MgO and/or NaF.

As used herein, if not defined more specifically in a particularcontext, the designation of the colors of emitted and/or absorbed lightis as follows:

violet: wavelength range of >380-420 nm;deep blue: wavelength range of >420-475 nm;sky blue: wavelength range of >475-500 nm;green: wavelength range of >500-560 nm;yellow: wavelength range of >560-580 nm;orange: wavelength range of >580-620 nm;red: wavelength range of >620-800 nm.

With respect to emitter compounds, such colors refer to the emissionmaximum λ_(max) ^(PMMA) of a poly(methyl methacrylate) (PMMA) film with10% by weight of the emitter. Therefore, exemplarily, a deep blueemitter has an emission maximum λ_(max) ^(PMMA) in the range of from 420to 475 nm, a sky blue emitter has an emission maximum λ_(max) ^(PMMA) inthe range of from 475 to 500 nm, a green emitter has an emission maximumλ_(max) ^(PMMA) in a range of from 500 to 560 nm, a red emitter has anemission maximum λ_(max) ^(PMMA) in a range of from 620 to 800 nm.

A deep blue emitter may preferably have an emission maximum λ_(max)^(PMMA) of not more than 475 nm, more preferably below 470 nm, even morepreferably below 465 nm or even below 460 nm. It will typically be above420 nm, preferably above 430 nm, more preferably of at least 440 nm. Ina preferred embodiment, the device exhibits an emission maximumλ_(max)(D) of 420 to 475 nm, 430 to 470 nm, 440 to 465 nm, or 450 to 460nm. In a preferred embodiment, the device exhibits an emission maximumλ_(max)(D) of 440 to 475 nm. In a preferred embodiment, the deviceexhibits an emission maximum λ_(max)(D) of 450 to 470 nm.

Accordingly, a further embodiment of the present invention relates to anOLED, which exhibits an external quantum efficiency at 1000 cd/m² ofmore than 10%, more preferably of more than 13%, more preferably of morethan 15%, even more preferably of more than 18% or even more than 20%and/or exhibits an emission maximum between 420 nm and 500 nm,preferably between 430 nm and 490 nm, more preferably between 440 nm and480 nm, even more preferably between 450 nm and 470 nm and/or exhibits aLT80 value at 500 cd/m² of more than 100 h, preferably more than 200 h,more preferably more than 400 h, even more preferably more than 750 h oreven more than 1000 h.

A further embodiment of the present invention relates to an OLED, whichemits light at a distinct color point. According to the presentinvention, the OLED emits light with a narrow emission band (small fullwidth at half maximum (FWHM)). In a preferred embodiment, the OLEDaccording to the invention emits light with a FWHM of the main emissionpeak of below 0.30 eV, more preferably of below 0.25 eV, even morepreferably of below 0.20 eV or even below 0.18 eV.

A further aspect of the present invention relates to an OLED, whichemits light with CIEx and CIEy color coordinates close to the CIEx(=0.131) and CIEy (=0.046) color coordinates of the primary color blue(CIEx=0.131 and CIEy=0.046) as defined by ITU-R Recommendation BT.2020(Rec. 2020) and thus is suited for the use in Ultra High Definition(UHD) displays, e.g. UHD-TVs. In commercial applications, typicallytop-emitting (top-electrode is transparent) devices are used, whereastest devices as used throughout the present application representbottom-emitting devices (bottom-electrode and substrate aretransparent). The CIEy color coordinate of a blue device can be reducedby up to a factor of two, when changing from a bottom- to a top-emittingdevice, while the CIEx remains nearly unchanged (Okinaka et al., Societyfor Information Display International Symposium Digest of TechnicalPapers, 2015, 46(1):312-313, DOI:10.1002/sdtp.10480). Accordingly, afurther aspect of the present invention relates to an OLED, whoseemission exhibits a CIEx color coordinate of between 0.02 and 0.30,preferably between 0.03 and 0.25, more preferably between 0.05 and 0.20or even more preferably between 0.08 and 0.18 or even between 0.10 and0.15 and/or a CIEy color coordinate of between 0.00 and 0.45, preferablybetween 0.01 and 0.30, more preferably between 0.02 and 0.20 or evenmore preferably between 0.03 and 0.15 or even between 0.04 and 0.10.

As used throughout the present application, the terms “aryl” and“aromatic” may be understood in the broadest sense as any mono-, bi- orpolycyclic aromatic moieties. If not otherwise indicated, an aryl mayalso be optionally substituted by one or more substituents which areexemplified further throughout the present application. Accordingly, theterm “arylene” refers to a divalent residue that bears two binding sitesto other molecular structures and thereby serving as a linker structure.As used throughout the present application, the terms “heteroaryl” and“heteroaromatic” may be understood in the broadest sense as any mono-,bi- or polycyclic heteroaromatic moieties that include at least oneheteroatom, in particular which bear from one to three heteroatoms peraromatic ring.

Exemplarily, a heteroaromatic compound may be pyrrole, furan, thiophene,imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine andpyrimidine, and the like. If not otherwise indicated, a heteroaryl mayalso be optionally substituted by one or more substituents which areexemplified further throughout the present application. Accordingly, theterm “heteroarylene” refers to a divalent residue that bears two bindingsites to other molecular structures and thereby serving as a linkerstructure.

As used throughout the present application, the term “alkyl” may beunderstood in the broadest sense as both, linear or branched chain alkylresidue. Preferred alkyl residues are those containing from one tofifteen carbon atoms. Exemplarily, an alkyl residue may be methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and the like. Ifnot otherwise indicated, an alkyl may also be optionally substituted byone or more substituents which are exemplified further throughout thepresent application. Accordingly, the term “alkylene” refers to adivalent residue that bears two binding sites to other molecularstructures and thereby serving as a linker structure.

If not otherwise indicated, as used herein, in particular in the contextof aryl, arylene, heteroaryl, alkyl and the like, the term “substituted”may be understood in the broadest sense. Preferably, such substitutionmeans a residue selected from the group consisting of C₁-C₂₀-alkyl,C₇-C₁₉-alkaryl, and C₆-C₁₈-aryl. Accordingly, preferably, no chargedmoiety, more preferably no functional group is present in suchsubstitution.

It will be noticed that hydrogen can, at each occurrence, be replaced bydeuterium.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. The layers in the context ofthe present invention, including the light-emitting layer B, mayoptionally be prepared by means of liquid processing (also designated as“film processing”, “fluid processing”, “solution processing” or “solventprocessing”). This means that the components comprised in the respectivelayer are applied to the surface of a part of a device in liquid state.Preferably, the layers in the context of the present invention,including the light-emitting layer B, may be prepared by means ofspin-coating. This method well-known to those skilled in the art allowsobtaining thin and (essentially) homogeneous layers.

Alternatively, the layers in the context of the present invention,including the light-emitting layer B, may be prepared by other methodsbased on liquid processing such as, e.g., casting (e.g., drop-casting)and rolling methods, and printing methods (e.g., inkjet printing,gravure printing, blade coating). This may optionally be carried out inan inert atmosphere (e.g., in a nitrogen atmosphere).

In another preferred embodiment, the layers in the context of thepresent invention may be prepared by any other method known in the art,including but not limited to vacuum processing methods well-known tothose skilled in the art such as, e.g., thermal (co-)evaporation,organic vapor phase deposition (OVPD), and deposition by organic vaporjet printing (OVJP).

When preparing layers by means of liquid processing, the solutionsincluding the components of the layers (i.e., with respect to thelight-emitting layer B of the present invention, at least one hostcompound H^(B) and, typically, at least one first TADF material E^(B),at least one second TADF material S^(B) and optionally one or more otherhost compounds H^(B2)) may further comprise a volatile organic solvent.Such volatile organic solvent may optionally be one selected from thegroup consisting of tetrahydrofuran, dioxane, chlorobenzene, diethyleneglycol diethyl ether, 2-(2-ethoxyethoxy)ethanol, gamma-butyrolactone,N-methyl pyrrolidinon, ethoxyethanol, xylene, toluene, anisole,phenetol, acetonitrile, tetrahydrothiophene, benzonitrile, pyridine,trihydrofuran, triarylamine, cyclohexanone, acetone, propylenecarbonate, ethyl acetate, benzene and PGMEA (propylen glycol monoethylether acetate). Also a combination of two or more solvents may be used.After applied in liquid state, the layer may subsequently be driedand/or hardened by any means of the art, exemplarily at ambientconditions, at increased temperature (e.g., about 50° C. or about 60°C.) or at diminished pressure.

Optionally, an organic electroluminescent device (e.g., an OLED) mayexemplarily be an essentially white organic electroluminescent device ora blue organic electroluminescent device. Exemplarily such white organicelectroluminescent device may comprise at least one (deep) blue emittercompound (e.g., TADF material E^(B)) and one or more emitter compoundsemitting green and/or red light. Then, there may also optionally beenergy transmittance between two or more compounds as described above.

The organic electroluminescent device as a whole may also form a thinlayer of a thickness of not more than 5 mm, more than 2 mm, more than 1mm, more than 0.5 mm, more than 0.25 mm, more than 100 μm, or more than10 μm.

An organic electroluminescent device (e.g., an OLED) may be asmall-sized (e.g., having a surface not larger than 5 mm², or even notlarger than 1 mm²), medium-sized (e.g., having a surface in the range of0.5 to 20 cm²), or a large-sized (e.g., having a surface larger than 20cm²). An organic electroluminescent device (e.g., an OLED) according tothe present invention may optionally be used for generating screens, aslarge-area illuminating device, as luminescent wallpaper, luminescentwindow frame or glass, luminescent label, luminescent poser or flexiblescreen or display. Next to the common uses, an organicelectroluminescent device (e.g., an OLED) may exemplarily also be usedas luminescent films, “smart packaging” labels, or innovative designelements. Further they are usable for cell detection and examination(e.g., as bio labelling).

One of the main purposes of an organic electroluminescent device is thegeneration of light. Thus, the present invention further relates to amethod for generating light of a desired wavelength range, comprisingthe step of providing an organic electroluminescent device according toany the present invention.

As laid out above, it was surprisingly found that the organicelectroluminescent device of the present invention bears particularlygood technical properties, such as longer lifetime, good quantum yieldsand desirable emission properties. In particular lifetime issignificantly and unexpectedly increased.

Accordingly, a further aspect of the present invention relates to theuse of a thermally activated delayed fluorescence (TADF) material E^(B)in combination with at least one triplet-triplet annihilation (TTA)material H^(N) and at least one organic near-range-charge-transfer(NRCT) emitter S^(B) in a light-emitting layer B of an organicelectroluminescent device, which is preferably characterized asdescribed herein, for increasing the lifetime of the organicelectroluminescent device.

Therefore, the present invention also relates to the use atriplet-triplet annihilation (TTA) material H^(N) in combination with atleast one thermally activated delayed fluorescence (TADF) material E^(B)and at least one organic near-range-charge-transfer (NRCT) emitter S^(B)in a light-emitting layer B of an organic electroluminescent device,which is preferably characterized as described herein, for increasingthe lifetime of the organic electroluminescent device.

Therefore, the present invention also relates to the use an organicnear-range-charge-transfer (NRCT) emitter S^(B) in combination with atleast one thermally activated delayed fluorescence (TADF) material E^(B)and at least one triplet-triplet annihilation (TTA) material H^(N) in alight-emitting layer B of an organic electroluminescent device, which ispreferably characterized as described herein, for increasing thelifetime of the organic electroluminescent device.

In other words, the present invention also relates to a method forincreasing lifetime of an organic electroluminescent device, said methodcomprising the step of combining in a light-emitting layer B:

a triplet-triplet annihilation (TTA) material H^(N),a thermally activated delayed fluorescence (TADF) material E^(B),an organic near-range-charge-transfer (NRCT) emitter S^(B), andoptionally one or more further materials such as those selected from thegroup consisting of one or more hosts and one or more solvents.

This step of combining the materials in a light-emitting layer B may beperformed by any means such as mixing the components and/orco-depositing such.

As used herein, the term “lifetime” may be understood in the broadestsense as the operating time in which still high emission of lightintensity is obtained. Preferably, lifetime may be characterized as theoperating time in which the light emission intensity decreases to 95% ofthe initial light emission intensity (LT95). It will be understood thatcomparable values are obtainable when comparable conditions are used(for example emission at 15 mA/cm² at room temperature).

As used herein, the term “increasing lifetime” and analogous expressionsmay be understood in the broadest sense as extending the lifetime whenlight is emitted at comparable conditions (current density, lightemission, temperature, etc). when compared to a comparable devicewherein one of the materials in the light-emitting layer B (e.g., H^(N),E^(B), or S^(B)) is missing.

In a preferred, the lifetime (LT95) is increased by at least 10%, atleast 20%, at least 30%, at least 40%, at least 50%, at least 75%, atleast 1.5 fold, at least 2 fold, at least 5 fold, or even 10 fold orlonger.

Accordingly, a further aspect of the present invention relates to amethod for generating light of a desired wavelength range, comprisingthe steps of

-   (i) providing an organic electroluminescent device according to the    present invention; and-   (ii) applying an electrical current to said organic    electroluminescent device.

A further aspect of the present invention relates to a process of makingthe organic electroluminescent devices by assembling the elementsdescribed above. The present invention also relates to a method forgenerating blue, green, yellow, orange, red or white light, inparticular blue or white light by using said organic electroluminescentdevice.

The Examples and claims further illustrate the invention.

EXAMPLES Cyclic Voltammetry

Cyclic voltammograms of solutions having concentration of 10⁻³ mol/l ofthe organic molecules in dichloromethane or a suitable solvent and asuitable supporting electrolyte (e.g. 0.1 mol/l of tetrabutylammoniumhexafluorophosphate) are measured. The measurements are conducted atroom temperature and under nitrogen atmosphere with a three-electrodeassembly (Working and counter electrodes: Pt wire, reference electrode:Pt wire) and calibrated using FeCp₂/FeCp₂ ₊ as internal standard. HOMOdata was corrected using ferrocene as internal standard against SCE.

Density Functional Theory Calculation

Molecular structures are optimized employing the BP86 functional and theresolution of identity approach (RI). Excitation energies are calculatedusing the (BP86) optimized structures employing Time-Dependent DFT(TD-DFT) methods. Orbital and excited state energies are calculated withthe B3LYP functional. Def2-SVP basis sets (and a m4-grid for numericalintegration were used. The Turbomole program package was used for allcalculations.

Photophysical Measurements

Sample pretreatment: Spin-coatingApparatus: Spin150, SPS euro.

The sample concentration is 10 mg/ml, dissolved in a suitable solvent.

Program: 1) 3 s at 400 U/min; 20 s at 1000 U/min at 1000 Upm/s. 3) 10 sat 4000 U/min at 1000 Upm/s. After coating, the films are tried at 70°C. for 1 min.Photoluminescence spectroscopy and TCSPC (Time-correlated single-photoncounting) Steady-state emission spectroscopy is recorded using a HoribaScientific, Modell FluoroMax-4 equipped with a 150 W Xenon-Arc lamp,excitation- and emissions monochromators and a Hamamatsu R928photomultiplier and a time-correlated single-photon counting option.Emissions and excitation spectra are corrected using standard correctionfits.

Excited state lifetimes are determined employing the same system usingthe TCSPC method with FM-2013 equipment and a Horiba Yvon TCSPC hub.

Excitation Sources:

NanoLED 370 (wavelength: 371 nm, puls duration: 1.1 ns)NanoLED 290 (wavelength: 294 nm, puls duration: <1 ns)SpectraLED 310 (wavelength: 314 nm)SpectraLED 355 (wavelength: 355 nm).Data analysis (exponential fit) was done using the software suiteDataStation and DAS6 analysis software. The fit is specified using thechi-squared-test.

Photoluminescence Quantum Yield Measurements

For photoluminescence quantum yield (PLQY) measurements an Absolute PLQuantum Yield Measurement C9920-03G system (Hamamatsu Photonics) isused. Quantum yields and CIE coordinates were determined using thesoftware U6039-05 version 3.6.0. Emission maxima are given in nm,quantum yields 4) in % and CIE coordinates as x,y values.

PLQY was determined using the following protocol:

-   -   1) Quality assurance: Anthracene in ethanol (known        concentration) is used as reference    -   2) Excitation wavelength: the absorption maximum of the organic        molecule is determined and the molecule is excited using this        wavelength    -   3) Measurement        -   Quantum yields are measured for sample of solutions or films            under nitrogen atmosphere. The yield is calculated using the            equation:

$\Phi_{PL} = {\frac{n_{photon},{emited}}{n_{photon},{absorbed}} = \frac{\int{{\frac{\lambda}{hc}\left\lbrack {{{Int}_{emitted}^{sample}(\lambda)} - {{Int}_{absorbed}^{sample}(\lambda)}} \right\rbrack}d\lambda}}{\int{{\frac{\lambda}{hc}\left\lbrack {{{Int}_{emitted}^{reference}(\lambda)} - {{Int}_{absorbed}^{reference}(\lambda)}} \right\rbrack}d\lambda}}}$

-   -   wherein n_(photon) denotes the photon count and Int. is the        intensity.

Production and Characterization of Organic Electroluminescence Devices

Via vacuum-deposition methods OLED devices comprising organic moleculesaccording to the invention can be produced. If a layer contains morethan one compound, the weight-percentage of one or more compounds isgiven in %. The total weight-percentage values amount to 100%, thus if avalue is not given, the fraction of this compound equals to thedifference between the given values and 100%.

The not fully optimized OLEDs are characterized using standard methodsand measuring electroluminescence spectra, the external quantumefficiency (in %) in dependency on the intensity, calculated using thelight detected by the photodiode, and the current. The OLED devicelifetime is extracted from the change of the luminance during operationat constant current density. The LT50 value corresponds to the time,where the measured luminance decreased to 50% of the initial luminance,analogously LT80 corresponds to the time point, at which the measuredluminance decreased to 80% of the initial luminance, LT97 to the timepoint, at which the measured luminance decreased to 97% of the initialluminance etc.

Accelerated lifetime measurements are performed (e.g. applying increasedcurrent densities). Exemplarily LT80 values at 500 cd/m² are determinedusing the following equation:

${{LT}80\left( {500\frac{{cd}^{2}}{m^{2}}} \right)} = {{LT}80\left( L_{0} \right)\left( \frac{L_{0}}{500\frac{{cd}^{2}}{m^{2}}} \right)^{1.6}}$

wherein L₀ denotes the initial luminance at the applied current density.

The values correspond to the average of several pixels (typically two toeight), the standard deviation between these pixels is given. Figuresshow the data series for one OLED pixel.

Example D1 and Comparative Examples C1

TABLE 1 Properties of the materials. Example compound S1 [eV] T1 [eV]λ_(max) ^(PMMA) [nm] TTA material H^(N) TTA1 3.16 TADF material E^(B)TADF1 2.87 2.80 476 NRCT emitter S^(B) NRCT1 2.65 2.47 495

TABLE 2 Setup of an example organic electroluminescent device (OLED),wherein different ingredients were co-deposited in layer 5 (allpercentages refer to weight percent) Layer Thickness D1 C1 9 100 nm AlAl 8 2 nm Liq Liq 7 11 nm NBPhen NBPhen 6 20 nm ET1 ET1 5 20 nm TTA1(92%): TTA1 (99%): TADF1 (7%): NRCT1 (1%) NRCT1 (1%) 4 10 nm HT2 HT2 350 nm HT1 HT1 2 7 nm HAT-CN HAT-CN 1 50 nm ITO ITO substrate glass glass

Device D1 yielded an external quantum efficiency (EQE) at 1000 cd/m² of7.03±0.05% and an LT95 value at 15 mA/cm² of 11.2 h. The emissionmaximum is at 488 nm with a FWHM of 28 nm at 3.4 V.

Comparative device C1 comprise the same layer arrangement as device D1,except that the emitting layer of C1 contains only TTA1 and NRCT1.

Device C1 yielded an external quantum efficiency (EQE) at 1000 cd/m² of9.18±0.08% and an LT95 value at 15 mA/cm² of 0.9 h. The emission maximumis at 488 nm with a FWHM of 28 nm at 3.4 V.

In comparison to device C1, device D1 shows an EQE at 1000 cd/m², whichis reduced by a factor of 1.31, while the LT95 value at 15 mA/cm² isincreased by a factor of 12.4, while for both devices, i.e. C1 and D1,the emission maximum and FWHM, measured at 3.4 V, remain unchanged.

Examples D2 and Comparative Example C2

TABLE 3 Properties of the materials. Example compound S1 [eV] T1 [eV]λ_(max) ^(PMMA) [nm] TTA material H^(N) TTA1 3.16 TADF material E^(B)TADF2 2.90 2.86 468 NRCT emitter S^(B) NRCT2 2.62 2.83 458

For TADF2, the S1, T1 and I_(max) ^(PMMA) values were measured at aconcentration of 10% in PMMA.

TABLE 4 Setup of an example organic electroluminescent device (OLED)(the percentages refer to weight percent) Layer Thickness D2 C2 9 100 nmAl Al 8 2 nm Liq Liq 7 11 nm NBPhen NBPhen 6 20 nm ET1 ET1 5 20 nm TTA1(92%): TTA1 (99%): TADF2 (7%): NRCT2 (1%) NRCT2 (1%) 4 10 nm HT2 HT2 350 nm HT1 HT1 2 7 nm HAT-CN HAT-CN 1 50 nm ITO ITO substrate glass glass

Device D2 yielded an external quantum efficiency (EQE) at 1000 cd/m² of7.64±0.03% and an LT95 value at 15 mA/cm² of 16.2 h. The emissionmaximum is at 460 nm with a FWHM of 26 nm at 4.1 V.

Comparative device C2 comprise the same layer arrangement as device D2,except that the emitting layer of C2 contains only TTA1 and NRCT2.

Device C2 yielded an external quantum efficiency (EQE) at 1000 cd/m² of9.81±0.02% and an LT95 value at 15 mA/cm² of 2.6 h. The emission maximumis at 460 nm with a FWHM of 26 nm at 4.2 V.

In comparison to device C2, device D2 shows an EQE at 1000 cd/m², whichis reduced by a factor of 1.28, while the LT95 value at 15 mA/cm² isincreased by a factor of 6.2, while for both devices, i.e. C2 and D2,the emission maximum and FWHM, measured at 4.1 V and 4.2 V,respectively, remain unchanged.

What is claimed is:
 1. An organic electroluminescent device comprising alight-emitting layer B comprising: (i) a first compound H^(N), which hasa lowermost excited singlet state energy level S1^(N), a lowermostexcited triplet state energy level T1^(N), (ii) a second compound E^(B),which has a lowermost excited singlet state energy level S1^(E) and alowermost excited triplet state energy level T1^(E), and (iii) a thirdcompound S^(B), which has a lowermost excited singlet state energy levelS1^(S) and a lowermost excited triplet state energy level T1^(S) whereinthe relations expressed by the following formulas (1) to (3) apply:S1^(E) >S1^(S)  (1)S1^(N) >S1^(S)  (2)S1^(S)<2.95 eV  (3).
 2. The organic electroluminescent device accordingto claim 1, wherein the second compound E^(B) exhibits a ΔE_(ST) value,which corresponds to the energy difference between the lowermost excitedsinglet state (S1) and the lowermost excited triplet state (T1), of lessthan 0.4 eV; and wherein the third compound S^(B) exhibits an emissionwith a full width at half maximum (FWHM) below 0.35 eV, in PMMA with 5%by weight of the third compound S^(B).
 3. The organic electroluminescentdevice according to claim 1, wherein said organic electroluminescentdevice is a device selected from the group consisting of an organiclight emitting diode, a light emitting electrochemical cell, and alight-emitting transistor.
 4. The organic electroluminescent deviceaccording to claim 1, wherein the second compound E^(B) is an organicTADF material.
 5. The organic electroluminescent device according toclaim 1, wherein the device exhibits an emission maximum λ_(max)(D) of440 to 475 nm.
 6. The organic electroluminescent device according toclaim 1, wherein the light-emitting layer B comprises: (i) 10-96.5% byweight of the first compound H^(N); (ii) 3-50% by weight of the secondcompound E^(B); and (iii) 0.5-30% by weight of the third compound S^(B);and (iv) optionally 0-74% by weight of one or more solvents.
 7. Theorganic electroluminescent device according to claim 1, wherein thelight-emitting layer B comprises: (i) 40-74% by weight of the firstcompound H^(N); (ii) 15-30% by weight of the second compound E^(B); and(iii) 1-5% by weight of the third compound S^(B); and (iv) optionally0-34% by weight of one or more solvents.
 8. The organicelectroluminescent device according to claim 1, wherein the firstcompound H^(N) is an anthracene derivative.
 9. The organicelectroluminescent device according to claim 1, wherein the thirdcompound S^(B) comprises a structure according to Formula I-NRCT:

wherein is 0 or 1; m=1-o; X¹ is N or B; X² is N or B; X³ is N or B; W isselected from the group consisting of Si(R^(3S))₂, C(R^(3S))₂ andBR^(3S); each of R^(1S), R^(2S) and R^(3S) is independently selectedfrom the group consisting of: C₁-C₅-alkyl, which is optionallysubstituted with one or more substituents R^(6S); C₆-C₆₀-aryl, which isoptionally substituted with one or more substituents R^(6S); andC₃-C₅₇-heteroaryl, which is optionally substituted with one or moresubstituents R^(6S); each of R^(I), R^(II), R^(III), R^(IV), R^(V),R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) is independentlyselected from the group consisting of: hydrogen, deuterium, N(R^(5S))₂,OR^(5S), Si(R^(5S))₃, B(OR^(5S))₂, OSO₂R^(5S), CF₃, CN, halogen,C₁-C₄₀-alkyl, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S); C₁-C₄₀-alkoxy, which is optionallysubstituted with one or more substituents R^(5S) and wherein one or morenon-adjacent CH₂-groups are each optionally substituted byR^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂, Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S,C═Se, C═NR^(5S), P(═O)(R^(5S)), SO, SO₂, NR^(5S), O, S or CONR^(5S);C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S); C₂-C₄₀-alkenyl, which is optionallysubstituted with one or more substituents R^(5S) and wherein one or morenon-adjacent CH₂-groups are each optionally substituted byR^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂, Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S,C═Se, C═NR^(5S), P(═O)(R^(5S)), SO, SO₂, NR^(5S), O, S or CONR^(5S);C₂-C₄₀-alkynyl, which is optionally substituted with one or moresubstituents R^(5S) and wherein one or more non-adjacent CH₂-groups areeach optionally substituted by R^(5S)C═CR^(5S), C≡C, Si(R^(5S))₂,Ge(R^(5S))₂, Sn(R^(5S))₂, C═O, C═S, C═Se, C═NR^(5S), P(═O)(R^(5S)), SO,SO₂, NR^(5S), O, S or CONR^(5S); C₆-C₆₀-aryl, which is optionallysubstituted with one or more substituents R^(5S); and C₃-C₅₇-heteroaryl,which is optionally substituted with one or more substituents R^(5S);R^(5S) is at each occurrence independently from another selected fromthe group consisting of: hydrogen, deuterium, OPh, CF₃, CN, F,C₁-C₅-alkyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-alkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₁-C₅-thioalkoxy, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkenyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₂-C₅-alkynyl, wherein optionally one or more hydrogen atoms areindependently from each other substituted by deuterium, CN, CF₃, or F;C₆-C₁₈-aryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents; C₃-C₁₇-heteroaryl, which is optionallysubstituted with one or more C₁-C₅-alkyl substituents; N(C₆-C₁₈-aryl)₂,N(C₃-C₁₇-heteroaryl)₂; and N(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl); R^(6S) isat each occurrence independently from another selected from the groupconsisting of hydrogen, deuterium, OPh, CF₃, CN, F, C₁-C₅-alkyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₁-C₅-alkoxy, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₁-C₅-thioalkoxy, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₂-C₅-alkenyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₂-C₅-alkynyl, whereinoptionally one or more hydrogen atoms are independently from each othersubstituted by deuterium, CN, CF₃, or F; C₆-C₁₈-aryl, which isoptionally substituted with one or more C₁-C₅-alkyl substituents;C₃-C₁₇-heteroaryl, which is optionally substituted with one or moreC₁-C₅-alkyl substituents; N(C₆-C₁₈-aryl)₂, N(C₃-C₁₇-heteroaryl)₂; andN(C₃-C₁₇-heteroaryl)(C₆-C₁₈-aryl); wherein two or more of thesubstituents selected from the group consisting of R^(I), R^(II),R^(III), R^(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), andR^(XI) that are positioned adjacent to another may optionally each forma ring system with another, wherein the ring system is selected from thegroup consisting of mono- or polycyclic ring system, aliphatic ringsystem, aromatic ring system, benzo-fused ring system and combinationsthereof; and wherein at least one of X¹, X² and X³ is B and at least oneof X¹, X² and X³ is N.
 10. The organic electroluminescent deviceaccording to claim 9, wherein X¹ and X³ each are N and X² is B.
 11. Theorganic electroluminescent device according to claim 9, wherein X¹ andX³ each are B and X² is N.
 12. The organic electroluminescent deviceaccording to claim 9, wherein o=0.
 13. The organic electroluminescentdevice according to claim 9, wherein each of R^(I), R^(II), R^(III),R^(IV), R^(V), R^(VI), R^(VII), R^(VIII), R^(IX), R^(X), and R^(XI) isindependently selected from the group consisting of: hydrogen,deuterium, halogen, Me, ^(i)Pr, ^(t)Bu, CN, CF₃, Ph, which is optionallysubstituted with one or more substituents independently selected fromthe group consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph, pyridinyl,which is optionally substituted with one or more substituentsindependently selected from the group consisting of Me, ^(i)Pr, ^(t)Bu,CN, CF₃, and Ph, pyrimidinyl, which is optionally substituted with oneor more substituents independently selected from the group consisting ofMe, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph, carbazolyl, which is optionallysubstituted with one or more substituents independently selected fromthe group consisting of Me, ^(i)Pr, ^(t)Bu, CN, CF₃, and Ph, triazinyl,which is optionally substituted with one or more substituentsindependently selected from the group consisting of Me, ^(i)Pr, ^(t)Bu,CN, CF₃, and Ph, and N(Ph)₂; and R^(1S) and R^(2S) are eachindependently selected from the group consisting of C₁-C₅-alkyl, whichis optionally substituted with one or more substituents R^(6S);C₆-C₃₀-aryl, which is optionally substituted with one or moresubstituents R^(6S); and C₃-C₃₀-heteroaryl, which is optionallysubstituted with one or more substituents R^(6S).
 14. The organicelectroluminescent device according to claim 1, wherein the deviceexhibits an emission maximum λ_(max)(D) of 450 to 470 nm.
 15. Theorganic electroluminescent device according to claim 1, wherein thesecond compound E^(B) is a carbazole derivative.
 16. The organicelectroluminescent device according to claim 1, wherein the secondcompound E^(B) comprises a structure according to Formula I-TADF:

wherein n is 1 or 2; X is selected from the group of Ar^(EWG), CN orCF₃; Z is selected from the group of a direct bond, CR³R⁴, C═CR³R⁴, C═O,C═NR³, NR³, O, SiR³R⁴, S, S(O) and S(O)₂; Ar^(EWG) is selected from oneof Formulas IIa to IIk;

wherein # represents the binding site of the single bond linkingAr^(EWG) to the substituted central phenyl ring of Formula I-TADF; eachof R¹ and R² is independently from another selected from the groupconsisting of hydrogen, deuterium, C₁-C₅-alkyl, wherein one or morehydrogen atoms are optionally substituted by deuterium, and C₆-C₁₈-aryl,which is optionally substituted with one or more substituents R⁶; eachof R^(a), R³ and R⁴ is independently from another selected from thegroup consisting of: hydrogen, deuterium, N(R⁵)₂, OR⁵, SR⁵, Si(R⁵)₃,CF₃, CN, F, C₁-C₄₀-alkyl, which is optionally substituted with one ormore substituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; andC₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵; R⁵ is at each occurrence independently fromanother selected from the group consisting of hydrogen, deuterium,N(R⁶)₂, OR⁶, SR⁶, Si(R⁶)₃, CF₃, CN, F, C₁-C₄₀-alkyl, which is optionallysubstituted with one or more substituents R⁶ and wherein one or morenon-adjacent CH₂-groups are optionally substituted by R⁶C═CR⁶, C≡C,Si(R⁶)₂, Ge(R⁶)₂, Sn(R⁶)₂, C═O, C═S, C═Se, C═NR⁶, P(═O)(R⁶), SO, SO₂,NR⁶, O, S or CONR⁶; C₆-C₆₀-aryl, which is optionally substituted withone or more substituents R⁶; and C₃-C₅₇-heteroaryl, which is optionallysubstituted with one or more substituents R⁶; R⁶ is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, OPh, CF₃, CN, F, C₁-C₅-alkyl, wherein one or morehydrogen atoms are optionally, independently from each other substitutedby deuterium, CN, CF₃, or F; C₁-C₅-alkoxy, wherein one or more hydrogenatoms are optionally, independently from each other substituted bydeuterium, CN, CF₃, or F; C₁-C₅-thioalkoxy, wherein one or more hydrogenatoms are optionally, independently from each other substituted bydeuterium, CN, CF₃, or F; C₆-C₁₈-aryl, which is optionally substitutedwith one or more C₁-C₅-alkyl substituents; C₃-C₁₇-heteroaryl, which isoptionally substituted with one or more C₁-C₅-alkyl substituents;N(C₆-C₁₈-aryl)₂; N(C₃-C₁₇-heteroaryl)₂, andN(C₃-C₁₂-heteroaryl)(C₆-C₁₈-aryl); R^(d) is at each occurrenceindependently from another selected from the group consisting ofhydrogen, deuterium, N(R⁵)₂, OR^(S), SR^(S), Si(R⁵)₃, CF₃, CN, F,C₁-C₄₀-alkyl, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵;C₁-C₄₀-thioalkoxy, which is optionally substituted with one or moresubstituents R⁵ and wherein one or more non-adjacent CH₂-groups areoptionally substituted by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O,C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵; andC₆-C₆₀-aryl, which is optionally substituted with one or moresubstituents R⁵; C₃-C₅₇-heteroaryl which is optionally substituted withone or more substituents R⁵; wherein the substituents R^(a), R³, R⁴ orR⁵ independently from each other optionally may form a mono- orpolycyclic, aliphatic, aromatic and/or benzo-fused ring system with oneor more substituents R^(a), R³, R⁴ or R⁵ and wherein the one or moresubstituents R^(d) independently from each other optionally may form amono- or polycyclic, aliphatic, aromatic and/or benzo-fused ring systemwith one or more substituents R^(d).
 17. The organic electroluminescentdevice according to claim 1, wherein the device exhibits a CIEx colorcoordinate of between 0.02 and 0.30 and/or a CIEy color coordinate ofbetween 0.00 and 0.45.
 18. The organic electroluminescent deviceaccording to claim 1, wherein the second compound E^(B) and the thirdcompound S^(B) are both organic materials.